Apparatus for producing sound



March 27, 1928.

F. W. FALCK APPARATUS FOR PRODUCING SOUND Filed Feb. 18. 1924 PatentedMar. 27, 19 28.

UNITED s 'rArss 1,663,831" PAT NT OFFICE.

FRITZ w. FALGK," or Los ANGEIiES, CALIFORNIA, ASSIGNOR or ONE-HALF TDAVID M. PALMER, or os ANGELES, CALIFORNIA.

APrAnArns ron PRODUCING SOUND.

Application filed February 18, 1924. Serial No. 693,646.

.This invention relates to. improvements, in the arrangement and;connection of electrical apparatus for the production of sound and moreparticularly refers to anampllfying apparatus for use in connection witha detector circuit in a radio or wireless receiving apparatus, althoughit is intended to .coverthe improvedapparatus in whatever connection itis employed.

In a wireless or radial receiver for the production of sound, such as]speech or music, it is necessary to simultaneously handle an extremelyvwide range of frequencies such as from twenty-five cycles per second tosix thousand cycles per: second.

Thus the background which is necessary, in

orchestral or band music mainly. employs low: frequenciessuch as belowfour hundred cycles persecond, whereas the major volume of speech eithermale or female will range between two hundred and fifty cycles persecond and three hundred cycles persecond and certain .musical"instruments and .con stant soundsemploy frequencies around or abovefive thousand. cycles-per. second. In the customary transformer coupledvamplifiers, these different frequencies are not equally amplified withthe result that certain of. the frequencies-dominate the others and tendto repress the amplification of certain frequencies with the result thatthe produced sound is greatly i'distortedv and the orchestral and bandmusic appears tinny while the speech is given unnatural twang.

This distortion of sound in the general type of transformer coupledamplifiersis due to a number of causes, such as first, overloading ofthe transformers employed in the amplifiers with the result. that the.cores of the transformers become magnetized to or approaching thesaturation point, causing. distort-ion in. thecurrent dellvered to thesecondary of the transformer, and second, the vacuum or audion tubesemployed in the amplifier are overloaded, n such customary transformercoupled amplifiers with :the result that themore readily amplifiedfrequencies are emphasized and pressed so that the current deliveredfrom the vacuum or audion tubes into the plate circuit of thetransformers is. greatly distorted.

Air-object of this invention is to provide a the less readily amplifiedfrequencies are re- I a, means for .reducingthe load upon the amplifyingtubes so that. the tubes may properly amplify all the desired range offrequencies. Y Another object of this inventionis to provide means forreducing the load upon the amplifying transformers so that the cores ofthe transformers will not be magnetized to the saturation pointand'maylinduce inthe secondary of the. transformer the desired range of,frequencies without an accompanying distortion of the same.

Other objects of the present-invention are toprovide means orarrangement of apparams for producing distortion .,fr.ee amplificationwhich apparatus willbe simple in construction and operation.

According to the present invention overloading of the vacuum or audiontubes is eliminated by first, dividing the current to be handled intheamplifier to "a plurality of grid electrodes, in place of impressing theentire'current upon a single grid'and second, by providing a pluralityof separate parallel paths for the current leadingto such gridelectrodes. The present invention provides a means for taking the loadoff the transformers by utilizing in each stage of amplification aplurality of separate amplifying transformers having their primariesconnected in series with the preceding detector with parallelconnections so that the entire secondary current :loes not pass throughany single transformer. f i

I also provide such means or arrangement of apparatus that the potentialvariations of the separate grids of the amplifiers are maintainedsimilar,that is, the charges upon the grids are of like potential at anygiven instant and by this means I am enabled to provide a single or unitplate circuit for receiving the amplified current Which circuit may-bethus directly connected with either phones or loud speakers withoutemploying any auxiliary circuits or connections to couple they variouscurrents received from the different plate electrodes.

This invention will be readily understood from the following descriptionof' the accompanying drawings in which I have diagrammatically indicatedone form of apparatus in which the. several improvements of thisinventionare embodied.

tecting circuit. It is to be understoo,d,.,how.-

ever that theform of detecting circuithc loes not form an essential partofthe present.

invention, as the invention maybe employed with various differentdetecting,circuits, In the drawings 1 represents the ordinary groundedaerial. connected through a tuning coil 2, which in the diagram isindicated; as: a loose coupler with theiaerial connected/through theprimary core of the couplerand grounded as indicated at 4. The secondary5 isconnected as usualin agrid circui-ti through a grid leak 6 to.the'grid 7' of the detector VVQCUHIYLOI' audion tube 8. The coil 2 mayhave'thevariable condenser15f shunted across-the sec ondary. 5. Thegrid. circuit is completed through the filament9-of theidetector, whichis heatedby .Al' battery, by connecting the secondary 5 to the.negativezterminal-of the .A battery as indicated at 10.

11 indicatesthe plate of the-detectoiutube which is. connected.toa'point 12. #13 indicatesa: second point connected to afB bitttery atthe positive side, thernegative side :of the batterybeingzconnected tothe negative terminal of the A battery as indicated at 1.4. a i

When .the a detector is.- employed .without an amplifier; phones maybeconnected across points .12 and. 13, as indicated by dotted lines,whereuponztheiplate circuit is complete from the plate. 11 of. the tubethrough. the 1 phones and B battery and filament 9 of the tube.

When employing the apparatus, embodying-thisrinventionzas an amplifierfor such a detector 1 .unit, z a plurality of transformers are connectedin series inthe plate circuit of the-detector. In. this=case twotransformers land '16 are shown, although it is under stood that anynumberof transformers may be employedif desired, and particularly if theamplified unit is to be employed as the second .or third amplifierin acascade system of amplification,.-it may be desirable to employ-morethan twowtransformers. The transformers 15 and l6havetheir primaries17andj18i connected in series between the taps-12 and 1-3andaare:preferably: :positicned apart so .that thereiis no .inductiveconnection between thesame. .The secondai'ies 19 and 20 of thetransformers are connected to separate: grids.2 1:-and .22respectively,preferably located in the separate vacuum or aud-ion'amplifying tubes 23 and 24. The otherterminalsof thesecoridaries 19 and20 may be connected. together as inclicated at 24; and-lead through a Cbattery of from 3. to 8 volts and .hence connected to the negative'leadof the circuitfemplioyedfor heating .the filaments 26 and 27 of the separate tubes of the amplifier.: These filaments 26 and 27 may be heatedfrom the A batterry employed for the detector-"tube, 8 as indicated.

Thecircu it is arranged so that the grids 21 vand 22 will maintain likepotential variations of the amplified current. This is accomplished bythe arrangement of the circuit shown in whi c lthe terminals of thesecondary windings l9 and 20, adjacent those teriminals of'theiprimarywindings 17 and 18 which terminals are most directly coupled with the,plateull, aresthe terminals ,of the secondary, vwhichare connectedtoitheggri-ds 21 and: 22.

' By rthis'a arrangement the plate electrodes 28-and 29, respectively,of the tubes 23 aud24.

maybe directly connectedtogether andplead through the phones or loudspeaker: 30 without, the necessity; of .emplpying ,additional rectifyingcircuits. for j.oining...the.-'separate plates. The, plate circuit. .of.the amplifier is completed bybeing connected to theipositive of thezfiBbattery, henceleading to the fila= ments 26 and. 27 by the positive.lead to. such filaments NVhile Ihave shownxtheplate circuit ,of

the;- amplifying: unit connected tthrough phones or speaker 30, itis/understoodthatiin place of thespeaker 30 the. vplatecircuit mayinclude transformers. orotherzrneans; for cone necting. succeedingstagesof amplification in cascade or other-. .arrangement .1f desired. 7

If thesucceeding stages of amplificationare to employ the-principles. ofthis inventiomjt is preferable that". the succeeding.- higher stagesofamplification shouldemploy a pro.- gressively larger number oftransformers and amplifying tubes. I

Thexvarious constants of; the circuit are .not setforth .in specificdetail,- as. any. of .the

well madeiformsof the transformers, tubes 1.

or other parts illustrated may be-employed,

the construction of which is well understood in the'art.

Byemployingathe amplifier of ,-the present invention, .the variousrange, offrequencics will be much more uniformly; amplified than in thegeneral transformercoupled amplifiers and .this is accomplished. asshowncby a simpleform of apparatus.

4 While the embodiment herein describedis well suitedfor the purposeofthis'invention, it is not intendedato' limit the inventionzto' :theparticular. embodimentshownas various modifications may be made. in: thedetails primaries. disposed in. series. in :an output per--without'departing from ftlles spirit of the-,in- 'vention;

tion of said detector circuit and having their quency amplifyingcircuit, whereby the load secondaries connected to the grids of sepaoneach transformer is reduced to prevent 1 rate audions, said transformersbeing inadedistortion from saturation of the cores therequate toseparately handle the current Withof. out distortion the plates of saidaudions be- Signed at Los Angeles, Cal, this 23d day ing directlyconnected together so that the of January, 1924.

plates operate at the same potential and provide a unit output circuitfor said audio fre- FRITZ W. FALCK.

